ON THE REDSHIFT OF THE VERY HIGH ENERGY BLAZAR 3C 66A

Journal Article · Wed Mar 20 00:00:00 EDT 2013 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/766/1/35· OSTI ID:22167568

Furniss, A.; Williams, D. A. ^[1]; Fumagalli, M. ^[2]; Danforth, C. ^[3]; Prochaska, J. X. ^[4]

---

1. Santa Cruz Institute of Particle Physics and Department of Physics, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States)
2. Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)
3. CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, 389-UCB, Boulder, CO 80309 (United States)
4. Department of Astronomy and Astrophysics, UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)

As a bright gamma-ray source, 3C 66A is of great interest to the high-energy astrophysics community, having a potential for placing cosmological constraints on models for the extragalactic background light (EBL) and the processes which contribute to this photon field. No firm spectroscopic redshift measurement has been possible for this blazar due to a lack of intrinsic emission and absorption features in optical spectra. We present new far-ultraviolet spectra from the Hubble Space Telescope/Cosmic Origins Spectrograph (HST/COS) of the BL Lac object 3C 66A covering the wavelength range 1132-1800 A. The data show a smooth continuum with intergalactic medium absorption features which can be used to place a firm lower limit on the blazar redshift of z {>=} 0.3347. An upper limit is set by statistically treating the non-detection of additional absorbers beyond z = 0.3347, indicating a redshift of less than 0.41 at 99% confidence and ruling out z {>=} 0.444 at 99.9% confidence. We conclude by showing how the redshift limits derived from the COS spectra remove the potential for this gamma-ray emitting blazar to place an upper limit on the flux of the EBL using high energy data from a flare in 2009 October.

• OSTI ID: 22167568
• Journal Information: Astrophysical Journal, Vol. 766, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABSORPTION
ASTROPHYSICS
BL LACERTAE OBJECTS
EMISSION
FAR ULTRAVIOLET RADIATION
GAMMA SOURCES
LIMITING VALUES
PHOTONS
QUASARS
RED SHIFT
RELICT RADIATION
SPECTROMETERS
SUPERMASSIVE STARS
TELESCOPES
WAVELENGTHS